1. Field of the Invention
This invention relates to transparent impact-resistant thermoplastic molding materials of a rigid methylmethacrylate polymerizate A, a rigid styrene-acrylonitrile polymer B and a flexible graft copolymer C of alkylmethacrylate and optionally styrene grafted onto a grafting base.
2. Description of the Prior Art
Transparent, impact resistant thermoplastic molding materials have been described in (1) German Published Application Ser. No. 15 20 631, (2) U.S. Pat. No. 4,097,555, (3) British Pat. No. 1,139,588, (4) German Application Ser. No. 20 45 742, and (5) German Published Application Ser. No. 28 28 517.
Reference (1) relates to transparent, impact resistant molding masses in which styrene, acrylonitrile and certain quantities of methylmethacrylate are polymerized in the presence of styrene-butadiene mixtures. The transparency of the products produced in accordance with this reference depend on the processing temperature, yellow very strongly and have an extremely upleasant odor which greatly impairs use as packaging. Another negative factor is a very pronounced seam marking.
Reference (2) relates to transparent, thermoplastic molding materials which contain a rigid component consisting of a terpolymer of styrene, acrylonitrile and methylmethacrylate and a flexible component consisting of a styrene/butadiene(SB) block copolymer which is grafted with the same composition of the termonomers from the rigid component and the refraction index of which is thus adjusted to the rigid component. These molding materials also show a pronounced yellow coloration and have an unpleasant odor. In most cases the transparency does not meet the requirements.
References 3, 4 and 5 relate to transparent molding materials which are based on a mixture of polymethylmethacrylate and styrene-acrylonitrile copolymers as rigid components and a flexible component based on polybutadiene or a SB-rubber which is grafted with styrene and acrylonitrile. In 3 and 4, the transparency of the molding materials is greatly dependent upon the processing temperature. In the molding materials of reference 5, the transparency is guaranteed even if high temperature differences are incurred during processing. All of the molding materials of references 3, 4 and 5 display a slight yellow coloration and an unpleasant odor which is damaging in certain areas of application. A purpose of this invention was to develop molding materials which do not have the above mentioned negative factors.